German finance minister Wolfgang Schauble said it would be a folly to boost the EU's bail-out machinery (EFSF) beyond its â¬440bn lending limit by deploying leverage to up to â¬2 trillion, perhaps by raising funds from the European Central Bank.

"I don't understand how anyone in the European Commission can have such a stupid idea. The result would be to endanger the AAA sovereign debt ratings of other member states. It makes no sense," he said.

Mr Schauble told Washington to mind its own businesss after President Barack Obama rebuked EU leaders for failing to recapitalise banks and allowing the debt crisis to escalate to the point where it is "scaring the world".

"It's always much easier to give advice to others than to decide for yourself. I am well prepared to give advice to the US government," he said.

The comments risk irritating the White House. US Treasury Secretary Tim Geithner has been a key driver of plans to give the EFSF enough firepower to shore up Italy and Spain, fearing a drift into "cascading default, bank runs and catastrophic risk" without dramatic action.